A particularly advantageous application lies in the back bearing assemblies of alternators for motor vehicles.
Generally, the bearing proper of a bearing assembly is held against a support by means of capsules or washers made of plastic or of additional elements made of steel (e.g. a stop ring). Throughout the present specification, the term "alternator back bearing assembly" is used to mean the bearing assembly situated on an alternator at its end remote from the drive thereto.
Various solutions attempt to reconcile operating stiffness (axial support for the shaft) and ease of installation.
Nevertheless, the slack necessary during assembly and for operation without applying stress on the bearing is itself damaging and can lead to several types of defect under the effect of vibration at high speed.
In particular, the outer ring of the bearing can be subjected to rotation that causes the bearing assembly to be destroyed.
Also, axial slack in the bearing and vibration at high speed can cause the rolling paths on the rings to be destroyed.
The vibration and hammering due to such slack can also give rise to premature wear of the bearing and its housing in the bearing support.
Document FR-A-1 135 722 describes a bearing assembly for a rotary shaft machine, which assembly includes a ball or roller bearing mounted between a support and the shaft. The outer ring of the bearing is rigidly fixed to the support while the inner ring is capable of sliding relative to the shaft. A column made up of two plate-springs is interposed between the inner ring and a shoulder on the shaft for the purpose of exerting a force tending to move them apart so as to take up the operating axial slack. Nevertheless, plate-springs are very stiff in that they exhibit significant resilience only when subjected to high stresses. As a result, the axial slack is taken up only at the price of applying large axial stresses on the parts, and that is harmful to good operation of the bearing assembly.